Orbiting planets exert a gravitational pull on their host star, which results in a periodic variation of the star's velocity along the line of sight of observation. This wobbling effect can be inferred as radial velocity (RV) information, which is a measure of the associated wavelength shifts. Shortly after the detection of first exoplanet 51 Pegasi-b, [1]} recognized that stellar activity severely impacts the measurement of RVs. If the variable stellar surface phenomena influence the RV measurement (by modifying the line shape or its position), then exoplanet detectability and characterization are also affected.
These include stellar oscillations, granulation, spots, and faculae/plages, and long-term magnetic activity cycles[1]}, [3]}. The most confusing signals are those caused by the presence of active regions on the stellar
surface, which can show periodicities and amplitudes similar to the
ones generated by real planetary signals. Studies by [4]} and [5]} show that these signals may be harder to disentangle.
